Take a look at any reliable list of popes and tally those who took the name of John. You’ll come up with a count of 21, and yet the last bona fide pope by that name was St. John XXIII.

What gives?

Well, let’s just say it’s pretty complicated — in truth, very complicated. If you want the details, you’ll find a good overview on a Wikipedia page dedicated to the whole mess (yes, the numbering of Pope Johns has its own page), but it really boils down to a single pivotal papal goof.

The guy who we now remember as Pope John XXI was actually the nineteenth of that regnal name in the authentic Petrine line. Born in Portugal around 1215, the future pontiff, Pedro Julião, studied theology and medicine at the University of Paris, and his clerical rise coincided with his work as a physician. For a time, he taught medicine in Siena, and even served as personal physician to Pope Gregory X — the same pope who went on to appoint the learned doctor as Cardinal Bishop of Tusculum in 1273.

Gregory’s successor, Pope Adrian V, passed away in 1276 after a monthlong pontificate, and Cardinal Julião was elected to assume the papal mantle, choosing the name John. “He styled himself ‘XXI’,” writes church historian Hans Kühner, “as he assumed, incorrectly, an anti-pope, ‘John XX’, who in fact never existed.”

There it is: one of our missing popes — an apostolic cipher! The other one is John “XVI,” an antipope whose regnal number was retained as a sort of placeholder in the official rolls. Despite this knotty kerfuffle in continuity, John XXI seems to have capably carried out his papal duties, addressing internal ecclesial matters, for instance, brokering peace in the West, and reaching out to the Christian East.

However, he spent much of his short reign (8 months) pursuing his academic interests — medicine, theology, philosophy — and he even had a private study built for that purpose at the papal palace in Viterbo. Unfortunately, that study collapsed on the pope without warning on 20 May 1277, and he died as the result of his injuries.

For me, as a convert, the tale of John XXI is a valuable reminder of the indisputable datum that popes are fully human – and often bumblers, just like me. Yes, popes are the living signs of Church unity (LG 23), and, yes, they speak with the voice of Peter guided by the Holy Spirit when it comes to faith and morals. These were teachings that were so important in my conversion, as was the dogma of papal infallibility under certain circumstances. Yet, this infallibility only “extends as far as the deposit of divine Revelation itself” (CCC 891), and if we ever need confirmation of that limitation, John “XXI” and his mistaken moniker are conveniently emblazoned in the historical record for everyone’s elucidation.

Of course, Pope John can’t be blamed for not knowing about the sequencing and labeling blunders of his predecessors — any more than he can be blamed for not knowing of his private study’s structural weaknesses. But that’s the point, isn’t it? It’s not the Holy Spirit’s job to superintend such mundane matters, important as they may be. Instead, they’re up to us, with God’s grace, to sort out best we can. We do so by drawing on our talents, knowledge, and experience, cooperating with each other (including the pope) in promoting the common good, and embracing the lessons from our mistakes — either immediately, or, as a people, down the road.

And that last point is another lesson from John XXI: What happens in the Church today (including what popes do [or don’t do]) isn’t just about us — that is, those who happen to be living in the present. It’s only with hindsight that we can look back and account for John XXI’s self-referential and other slip-ups, but it’s also only with hindsight that we can look back and appreciate his positive accomplishments — and even those could be open to debate.

Yet, there’s no question that the same hindsight helps us see that John XXI, like all legitimate heirs to St. Peter, gave us a gift simply by accepting his office, for in so doing he became a living link in a chain of succession that not only connects us to Christ, but also embodies our connection to each other in Christ’s one Church. Ubi Petrus, ibi Ecclesia goes the Latin epigram — where Peter is, there is the Church — and it doesn’t much matter if we like him or how he carries out his duties. It doesn’t even matter what name he takes – or what number.

What matters, I think, is that pray for him. Like any fallible man, he needs us to.

Rick Becker is a husband, father of seven, nursing instructor, and religious educator. He serves on the nursing faculty at Bethel College in Mishawaka, Indiana. You can find more of Rick’s writing on his blog, God-Haunted Lunatic, and his Facebook page.